+ Added fuzzy name matching on install failures. (gstark/presidentbeef)

lib/rubygems/command.rb

@@ -146,15 +146,23 @@ def execute
   end
 
   ##
-  #
   # Display to the user that a gem couldn't be found and reasons why
-  def show_lookup_failure(gem_name, version, errors=nil)
+
+  def show_lookup_failure(gem_name, version, errors, domain)
     if errors and !errors.empty?
       alert_error "Could not find a valid gem '#{gem_name}' (#{version}), here is why:"
       errors.each { |x| say "          #{x.wordy}" }
     else
       alert_error "Could not find a valid gem '#{gem_name}' (#{version}) in any repository"
     end
+
+    unless domain == :local then # HACK
+      suggestions = Gem::SpecFetcher.fetcher.suggest_gems_from_name gem_name
+
+      unless suggestions.empty?
+        alert_error "Possible alternatives: #{suggestions.join(", ")}"
+      end
+    end
   end
 
   ##

lib/rubygems/commands/fetch_command.rb

@@ -52,7 +52,7 @@ def execute
       spec, source_uri = specs_and_sources.sort_by { |s,| s.version }.last
 
       if spec.nil? then
-        show_lookup_failure gem_name, version, errors
+        show_lookup_failure gem_name, version, errors, options[:domain]
         next
       end
 

lib/rubygems/commands/install_command.rb

@@ -128,7 +128,7 @@ def execute
         alert_error "Error installing #{gem_name}:\n\t#{e.message}"
         exit_code |= 1
       rescue Gem::GemNotFoundException => e
-        show_lookup_failure e.name, e.version, e.errors
+        show_lookup_failure e.name, e.version, e.errors, options[:domain]
 
         exit_code |= 2
       end

lib/rubygems/spec_fetcher.rb

@@ -1,13 +1,15 @@
 require 'rubygems/remote_fetcher'
 require 'rubygems/user_interaction'
 require 'rubygems/errors'
+require 'rubygems/text'
 
 ##
 # SpecFetcher handles metadata updates from remote gem repositories.
 
 class Gem::SpecFetcher
 
   include Gem::UserInteraction
+  include Gem::Text
 
   ##
   # The SpecFetcher cache dir.
@@ -181,6 +183,35 @@ def legacy_repos
     end
   end
 
+  ##
+  # Suggests a gem based on the supplied +gem_name+. Returns a string
+  # of the gem name if an approximate match can be found or nil
+  # otherwise. NOTE: for performance reasons only gems which exactly
+  # match the first character of +gem_name+ are considered.
+
+  def suggest_gems_from_name gem_name
+    gem_name        = gem_name.downcase
+    gem_starts_with = gem_name[0,1]
+    max             = gem_name.size / 2
+    specs           = list.values.flatten(1) # flatten(1) is 1.8.7 and up
+
+    matches = specs.map { |name, version, platform|
+      next unless Gem::Platform.match platform
+
+      distance = levenshtein_distance gem_name, name.downcase
+
+      next if distance >= max
+
+      return [name] if distance == 0
+
+      [name, distance]
+    }.compact
+
+    matches = matches.uniq.sort_by { |name, dist| dist }
+
+    matches.first(5).map { |name, dist| name }
+  end
+
   ##
   # Returns a list of gems available for each source in Gem::sources.  If
   # +all+ is true, all released versions are returned instead of only latest

lib/rubygems/text.rb

@@ -26,5 +26,40 @@ def format_text(text, wrap, indent=0)
     result.join("\n").gsub(/^/, " " * indent)
   end
 
+  # This code is based directly on the Text gem implementation
+  # Returns a value representing the "cost" of transforming str1 into str2
+  def levenshtein_distance str1, str2
+    s = str1
+    t = str2
+    n = s.length
+    m = t.length
+    max = n/2
+
+    return m if (0 == n)
+    return n if (0 == m)
+    return n if (n - m).abs > max
+
+    d = (0..m).to_a
+    x = nil
+
+    n.times do |i|
+      e = i+1
+
+      m.times do |j|
+        cost = (s[i] == t[j]) ? 0 : 1
+        x = [
+             d[j+1] + 1, # insertion
+             e + 1,      # deletion
+             d[j] + cost # substitution
+            ].min
+        d[j] = e
+        e = x
+      end
+
+      d[m] = x
+    end
+
+    return x
+  end
 end
 

test/test_gem_commands_install_command.rb

@@ -172,6 +172,29 @@ def test_execute_nonexistent
     assert_match(/ould not find a valid gem 'nonexistent'/, @ui.error)
   end
 
+  def test_execute_nonexistent_with_hint
+    misspelled="nonexistent_with_hint"
+    correctly_spelled="non_existent_with_hint"
+
+    util_setup_fake_fetcher
+    util_setup_spec_fetcher quick_gem(correctly_spelled, '2')
+
+    @cmd.options[:args] = misspelled
+
+    use_ui @ui do
+      e = assert_raises Gem::SystemExitException do
+        @cmd.execute
+      end
+      assert_equal 2, e.exit_code
+    end
+
+    expected = "ERROR:  Could not find a valid gem 'nonexistent_with_hint' (>= 0) in any repository
+ERROR:  Possible alternatives: non_existent_with_hint
+"
+
+    assert_equal expected, @ui.error
+  end
+
   def test_execute_prerelease
     util_setup_fake_fetcher(:prerelease)
     util_setup_spec_fetcher @a2, @a2_pre

test/test_gem_text.rb

@@ -19,4 +19,25 @@ def test_format_text_none
   def test_format_text_none_indent
     assert_equal "  text to wrap",    format_text("text to wrap", 40, 2)
   end
+
+  def test_levenshtein_distance_add
+    assert_equal 2, levenshtein_distance("zentest", "zntst")
+    assert_equal 2, levenshtein_distance("zntst", "zentest")
+  end
+
+  def test_levenshtein_distance_empty
+    assert_equal 5, levenshtein_distance("abcde", "")
+    assert_equal 5, levenshtein_distance("", "abcde")
+  end
+
+  def test_levenshtein_distance_remove
+    assert_equal 3, levenshtein_distance("zentest", "zentestxxx")
+    assert_equal 3, levenshtein_distance("zentestxxx", "zentest")
+  end
+
+  def test_levenshtein_distance_replace
+    assert_equal 2, levenshtein_distance("zentest", "ZenTest")
+    assert_equal 7, levenshtein_distance("xxxxxxx", "ZenTest")
+    assert_equal 7, levenshtein_distance("zentest", "xxxxxxx")
+  end
 end